<template>
    <div class="s-canvas">
      <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
  </template>
  <script>
  export default {
    name: 'SIdentify',
    props: {
      identifyCode: { // 默认注册码
        type: String,
        default: ''
      },
      fontSizeMin: { // 字体最小值
        type: Number,
        default: 25
      },
      fontSizeMax: { // 字体最大值
        type: Number,
        default: 35
      },
      backgroundColorMin: { // 验证码图片背景色最小值
        type: Number,
        default: 200
      },
      backgroundColorMax: { // 验证码图片背景色最大值
        type: Number,
        default: 220
      },
      dotColorMin: { // 背景干扰点最小值
        type: Number,
        default: 10
      },
      dotColorMax: { // 背景干扰点最大值
        type: Number,
        default: 60
      },
      contentWidth: { // 容器宽度
        type: Number,
        default: 122
      },
      contentHeight: { // 容器高度
        type: Number,
        default: 48
      }
    },
    methods: {
      // 生成一个随机数
      randomNum (min, max) {
        return Math.floor(Math.random() * (max - min) + min)
      },
      // 生成一个随机的颜色
      randomColor (min, max) {
        let r = this.randomNum(min, max)
        let g = this.randomNum(min, max)
        let b = this.randomNum(min, max)
        return 'rgb(' + r + ',' + g + ',' + b + ')'
      },
      drawPic () {
        let canvas = document.getElementById('s-canvas')
        let ctx = canvas.getContext('2d')
        ctx.textBaseline = 'bottom'
        // 绘制背景
        ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax)
        ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
        // 绘制文字
        for (let i = 0; i < this.identifyCode.length; i++) {
          this.drawText(ctx, this.identifyCode[i], i)
        }
        this.drawLine(ctx)
        this.drawDot(ctx)
      },
      drawText (ctx, txt, i) {
        ctx.fillStyle = this.randomColor(50, 160) // 随机生成字体颜色
        ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei' // 随机生成字体大小
        let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
        let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
        var deg = this.randomNum(-30, 30)
        // // 修改坐标原点和旋转角度
        ctx.translate(x, y)
        ctx.rotate(deg * 0)
        ctx.fillText(txt, 0, 0)
        // // 恢复坐标原点和旋转角度
        ctx.rotate(-deg * 0)
        ctx.translate(-x, -y)
      },
      drawLine (ctx) {
        // 绘制干扰线
        for (let i = 0; i < 4; i++) {
          ctx.strokeStyle = this.randomColor(100, 200)
          ctx.beginPath()
          ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
          ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
          ctx.stroke()
        }
      },
      drawDot (ctx) {
        // 绘制干扰点
        for (let i = 0; i < 30; i++) {
          ctx.fillStyle = this.randomColor(0, 255)
          ctx.beginPath()
          ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
          ctx.fill()
        }
      }
    },
    watch: {
      identifyCode () {
        this.drawPic()
      }
    },
    mounted () {
      this.drawPic()
    }
  }
  </script>
   
  <style scoped>
  #s-canvas{
    position: absolute;
    right: 0;
    bottom: 0;
    cursor: pointer;
  }
  </style>